| From da48524eb20662618854bb3df2db01fc65f3070c Mon Sep 17 00:00:00 2001 |
| From: Julien Tinnes <jln@google.com> |
| Date: Fri, 18 Mar 2011 15:05:21 -0700 |
| Subject: Prevent rt_sigqueueinfo and rt_tgsigqueueinfo from spoofing the signal code |
| |
| From: Julien Tinnes <jln@google.com> |
| |
| commit da48524eb20662618854bb3df2db01fc65f3070c upstream. |
| |
| Userland should be able to trust the pid and uid of the sender of a |
| signal if the si_code is SI_TKILL. |
| |
| Unfortunately, the kernel has historically allowed sigqueueinfo() to |
| send any si_code at all (as long as it was negative - to distinguish it |
| from kernel-generated signals like SIGILL etc), so it could spoof a |
| SI_TKILL with incorrect siginfo values. |
| |
| Happily, it looks like glibc has always set si_code to the appropriate |
| SI_QUEUE, so there are probably no actual user code that ever uses |
| anything but the appropriate SI_QUEUE flag. |
| |
| So just tighten the check for si_code (we used to allow any negative |
| value), and add a (one-time) warning in case there are binaries out |
| there that might depend on using other si_code values. |
| |
| Signed-off-by: Julien Tinnes <jln@google.com> |
| Acked-by: Oleg Nesterov <oleg@redhat.com> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
| |
| --- |
| kernel/signal.c | 16 ++++++++++++---- |
| 1 file changed, 12 insertions(+), 4 deletions(-) |
| |
| --- a/kernel/signal.c |
| +++ b/kernel/signal.c |
| @@ -2406,9 +2406,13 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, |
| return -EFAULT; |
| |
| /* Not even root can pretend to send signals from the kernel. |
| - Nor can they impersonate a kill(), which adds source info. */ |
| - if (info.si_code >= 0) |
| + * Nor can they impersonate a kill()/tgkill(), which adds source info. |
| + */ |
| + if (info.si_code != SI_QUEUE) { |
| + /* We used to allow any < 0 si_code */ |
| + WARN_ON_ONCE(info.si_code < 0); |
| return -EPERM; |
| + } |
| info.si_signo = sig; |
| |
| /* POSIX.1b doesn't mention process groups. */ |
| @@ -2422,9 +2426,13 @@ long do_rt_tgsigqueueinfo(pid_t tgid, pi |
| return -EINVAL; |
| |
| /* Not even root can pretend to send signals from the kernel. |
| - Nor can they impersonate a kill(), which adds source info. */ |
| - if (info->si_code >= 0) |
| + * Nor can they impersonate a kill()/tgkill(), which adds source info. |
| + */ |
| + if (info->si_code != SI_QUEUE) { |
| + /* We used to allow any < 0 si_code */ |
| + WARN_ON_ONCE(info->si_code < 0); |
| return -EPERM; |
| + } |
| info->si_signo = sig; |
| |
| return do_send_specific(tgid, pid, sig, info); |